This section is intended to provide a background to the various embodiments of the technology that are described in this disclosure. The description in this section may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and/or claims of this disclosure and is not admitted to be prior art by its inclusion in this section.
Radio communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such communication networks generally support communications for multiple UEs by sharing available network resources. One example of such a network is the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology standardized by the 3rd Generation Partnership Project (3GPP). UMTS includes a definition for a Radio Access Network (RAN), referred to as Universal Terrestrial Radio Access Network (UTRAN). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, supports various air interface standards, such as Wideband Code Division Multiple Access (WCDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks. As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with wireless communications. For example, UMTS based on WCDMA has been deployed in many places around the world. To ensure that this system remains competitive in the future, 3GPP began a project to define the long-term evolution of UMTS cellular technology. The specifications related to this effort are formally known as Evolved UMTS Terrestrial Radio Access (EUTRA) and Evolved UMTS Terrestrial Radio Access Network (EUTRAN), but are more commonly referred to by the name Long Term Evolution (LTE).
In LTE, two mechanisms are specified how a UE may request resources from a scheduling evolved NodeB (eNB): i) random access signaling and ii) scheduling request signaling.
Random Access in LTE
Random access (RA) is contention based and is generally used by the UE if it has no resources assigned to it. It should be appreciated that RA is also used by the UE if the UE is not uplink (UL) synchronized and the UE needs to obtain UL synchronization. An eNB generally announces the time-frequency location as well as other important parameters in its system information (SI). This enables a UE to send a message to the eNB using the Random Access Channel (RACH). In LTE the resources allocated for random access are 1 MHz wide and typically 1 ms long. However, in coverage limited situations also longer time slots for longer transmissions maybe reserved. As mentioned above, the parameters describing the RACH are typically signaled via system information. System information distribution in LTE is typically done via RRC (Radio Resource Configuration) signaling and dynamics in the random access channel configurations are relatively slow. Thus, it is generally difficult or at least challenging to change the configuration at immediate, or quick, traffic changes in the radio communication network.
Scheduling Request in LTE
Scheduling requests are dedicated (i.e. not contention based) resources that may be assigned to UEs enabling them to request resources from the eNB. Scheduling request resources are just a single bit and generally do not allow signaling of more information than information representing “I need UL resources”. A scheduling request is typically transmitted using one point of a QPSK constellation. If a UE does not request resources it does not transmit anything. The scheduling request is transmitted on the Physical Uplink Control Channel which spans 180 kHz in LTE. Scheduling request resources are also configured via RRC and changes to its configuration are therefore rather slow. Thus, it is generally difficult or at least challenging to change the configuration at immediate traffic changes in the radio communication network.
Contention Based Access in WiFi 802.11ad
Wi-Fi standard 802.11ad enables scheduled periods and Contention Based Access Periods (CBAP). Contention based access periods are not exclusively assigned to one UE but multiple ones and a UE generally needs to contend to gain access to the shared resource. Contention based access periods are announced in the Beacon Transmission Interval (BTI) which is used to broadcast system information in 802.11ad. The Beacon transmission interval maybe compared to the broadcast channel in LTE and is also a somewhat semi-static channel. Contention based access periods generally span 2 GHz in 802.11ad, i.e. the complete system bandwidth.
Flexible Transmit-Time-Interval (TTI)
With the data rates envisioned in so-called Ultra-Dense Networks (UDN)—in the order of 10 Gbps—it becomes feasible to convey complete Internet Protocol (IP) packets in one scheduling unit without Layer 2 (L2) segmentation. Avoiding L2 segmentation may lead to simpler protocol structures. IP packets generally vary in size and most dominating IP packet sizes are several ten bytes (IP control packets) and 1500 bytes (Maximum Transmission Unit (MTU) size of Ethernet). Fitting an IP packet into one scheduling unit therefore generally requires a Flexible TTI in time which would be shorter for smaller IP packets and longer for larger IP packets.
FIG. 1 illustrates a Flexible TTI frame structure. This figure only shows the time-domain and does not show resource granularity in frequency-domain. However, it should be appreciated that an FDM (Frequency Division Multiplex) component is supported, i.e. within a given portion of the total frame a UE may also be assigned only to a fraction of the complete bandwidth. An example of a frame structure is as follows: A frame is 100 μs long and is subdivided into several sub-frames of e.g. 12.5 μs each. In the frequency-domain the system bandwidth is portioned into sub-channels of e.g. 100 MHz.
Each data frame starts with a first zone 1, where control information is transmitted. Zone 1 is followed by another zone 2, which is the receive part (from the receiving node point of view). Finally, there is yet another zone, i.e. zone 3, which is the transmit part (also from the receiving node point of view). The control signaling comprises information related to which resources within zone 2 the receiving node should decode and on which resources the receiving node may transmit. The control signaling part and/or zone 2 may furthermore comprise acknowledgement bits from a node which received transmissions from this node in an earlier frame. If the control signaling does not utilize all resources of zone 1 it may be considered to assign empty resources of zone 1 to zone 2. Zone 2 generally comprises data transmitted to the node. Depending on the amount of data one, a few or all sub-frames within zone 2 may be assigned to the receiving node. The minimum scheduling unit is 1 sub-frame (time)×1 sub-channel (frequency)=12.5 μs×100 MHz. This unit is also referred to as Atomic Scheduling Unit (ASU). With a rather low spectrum efficiency of 1 bit/s/Hz one ASU may support 1250 bits≈150 bytes. If a node has resources assigned in zone 3 it may use these resources to transmit upon. Also in zone 3 the assigned resources are in multiples of one ASU. In addition to user data transmissions also acknowledgment bits in response to received data (either in this frame or if node processing is too slow in response to data received in an earlier frames) may be transmitted. The split, or division, between zone 2 and zone 3 is flexible. If there are no inter-node interference issues it is generally preferable that the partition between zone 2 and zone 3 is adjustable on a frame basis.
Generally speaking, all signaling schemes described herein (except the zone 2/zone 3 border) above may only be reconfigured on a relatively slow basis, since their respective configuration is of semi-static nature. Thus, this does not necessarily allow for an efficient use of currently unused resources (e.g. UL resources) by the UEs since the contention based channels may only be reconfigured relatively slowly.
Also, a radio access network node is generally aware of the buffer status in the transmission queues that are transmitted from the radio access network node to other UEs or other nodes. However, the radio access network node is typically not aware of the buffer status of remote queues, i.e. the buffer status of UEs and/or other nodes transmitting to the radio access network node. Therefore, the above-mentioned zone 3 may be unused or at least unnecessarily underutilized. In a radio communication network where a radio access network node schedules a UE or another node, this first radio access network node generally has to poll the UEs and/or other nodes scheduled by it so that these nodes may request resources if traffic arrives. This signaling is typically done via scheduling request signaling, buffer status reporting or random access signaling.